The function of integrated circuits in semiconductor chips may be adversely affected by electromagnetic or radioactive irradiation. The irradiation may generate free charge carriers in the semiconductor material, the charge carriers generating undesirable currents when potential differences are present. These currents give rise to a malfunction or at least a change in function in the integrated circuit. For applications relevant to security, semiconductor chips are therefore provided with protective structures which, for example, may be formed by shields on the top side of the chip. Shields of this type may be formed by protective layers comprising an electrically insulating material which is impermeable to radiation; instead, provision may also be made of suitably patterned electrical conductors which, apart from shielding, also make it possible to electronically detect irradiation. Various technical realizations of protective structures comprising sensors are known, the sensors being used to detect irradiation of a semiconductor chip. Sensors of this type are arranged in the vicinity of those regions of the integrated circuit which are adversely affected by irradiation. However, it has been shown that the irradiation may be focused in such a manner or, using masks, may be directed toward particular parts of the circuit in such a manner that although functional disturbances are produced, none of the sensors provided responds. This problem arises, in particular, in semiconductor memory elements such as, for example, in EEPROMs.
DE 196 01 390 C2 specifies a microchip having a light-sensitive element, which may be an element which changes its electrical properties when light is incident, the changed electrical properties being used to realize a switching function.
EP 0 874 401 A2 describes an interconnect, which is intended as an optical cover and is arranged in alternating mutually opposite directions, the interconnect covering the top side of the IC chip. A connected circuit checks the intactness of the cover on the basis of an electrical voltage applied to the interconnect.